This invention relates generally to subsurface well perforating apparatus and, more specifically to bullet perforating guns and a means for extending the useful life of the barrels used in these guns.
It has become common practice in the completion of oil and gas wells to perforate the well casing and the surrounding formations to bring a well into production. Bullet perforating guns have long been used for this purpose, especially in perforating formations of low compressive strength.
One of the major problems in the use of bullet perforating guns has been wear to and expansion of the barrels which results in "blow-bys" of the propellent gas, thereby reducing the bullet velocity and degrading the bullet performance. Eventually this wear and expansion renders the barrel useless, whch means that the barrel must discarded.
This and other disadvantages are overcome by the present invention which provides a relatively inexpensive wear member that is inserted into a relatively expensive outer member to form the barrel. This wear member reduces the wear to and expansion of the outer member, thereby extending the useful life of the outer member. The wear member can also be inserted into a previously worn or expanded outer member, thereby rehabilitating this outer member for further use.